Hot melt glue applicator



Nov. 14, 1967 G. H. LOCKWOOD 3,352,278

HOT MELT GLUE APPLICATOR Filed Feb. 1, 1965 5 Sheets-Sheet 1 INVENTOR.(iv Aw bi [aczwaoa 1967 G. H. LOCKWOOD HOT MELT GLUE APPLICATOR 3Sheets-Sheet 2 Filed Feb; 1, 1965 INVENTOR. 64W 19. Ava W000 Nov. 14,1967 5. H. LOCKWOOD 3,352,278

HOT MELT GLUE APPLICATOR Filed Feb. 1, 1965 3 Sheets-Sheet 5 INVENTOR.64 nviv fl. Z calm 00a yat r 22% I TTOiA/III United States Patent3,352,278 HOT MELT GLUE APPLICATOR Glynn H. Lockwood, Carmel, Calif.,assignor to The Tensor Corporation, a corporation of California FiledFeb. 1, 1965, Ser. No. 429,264 Claims. (Cl. 118-7) ABSTRACT OF THEDISCLOSURE A hot melt glue applicator has a reservoir open at one endand closed by a rotatable pattern wheel having a thin peripheral banddefining an annular volume in which is disposed a heater stationary onthe frame and heating the reservoir contents through the peripheralband. A thermostat in the reservoir is responsive to the conducted heatand controls the supply of glue to the reservoir.

My invention relates to means for utilizing glue originally in dry,approximately granular form, heating the glue to change it into a liquidform and then applying the liquid to devices to be glued, such as cartonflaps and the like.

A device of a related nature is shown in the copending application ofLockwood, Panzer, Schleicher and Hudson, Ser. No. 259,074 filed Feb. 18,1963.

In the present instance, it is primarily an object of the invention toprovide a hot melt glue applicator in which the glue, although normallydry and solid in form, is converted into a liquid and is transported andapplied in liquid form in an economical and efiicient fashion.

Another object of the invention is to provide a hot melt glue applicatorin which there is a carefully regulated supply of glue to the applicatorand in which the glue is well applied without becoming distributed inunwanted areas.

Another object of the invention is to provide a hot melt glue applicatorwhich can be utilized as a unit for installation on carton machines andthe like already in existence.

Another object of the invention is to provide a hot melt glue applicatorutilizing a relatively small number of parts and which is easilyaccessible for servicing and attention, but which is relatively ruggedand capable of operation for protracted periods without any difficulty.

Another object of the invention is to provide a hot melt glue applicatorin which the supply of glue to the applicator is automaticallymaintained.

Other objects together with the foregoing are attained in the embodimentof the invention described in the accompanying description andillustrated in the accompanying drawings, in which:

FIGURE 1 is a side elevation of the hot melt glue applicator constructedpursuant to the invention, certain portions being showndiagrammatically;

FIGURE 2 is a cross section on a vertical axial plane through theliquefying unit of the hot melt glue applicator;

FIGURE 3 is a plan of a portion of the structure shown in FIGURE 2,certain enclosures and covers being removed;

FIGURE 4 is a cross section through the drive mechanism as indicated bythe line 4-4 of FIGURE 1;

FIGURE 5 is a cross section through the applicator unit, the planes ofsection being indicated by the lines 55 of FIGURE 1; and

FIGURE 6 is a detailed cross section, the plane of which is indicated bythe line 6-6 of FIGURE 5.

The hot melt glue applicator pursuant to the invention is readilyinstalled in a number of different environments and in the presentinstance is illustrated as it is utilized ice for the application ofliquid glue to the lower surface 6 of a flap 7 extended from a carton 8.This carton is usually of cardboard or fiberboard an is appropriatelyadvanced on a conveyor 9 past the station at which the glue applicatoris disposed. A cam shoe 11 is a part of the carton handling mechanismand affords a backing for the flap 7. The carton handling mechanism isno part of the present invention and is illustrated as being of standardnature. The result of the carton handling mechanism is to advance thecarton 8 with the extended flap 7 travelling under the stationary camshoe 11 and past the glue applicator mechanism.

Partially for ease in manufacture, partially for flexibility ininstallation, and also for thermal reasons, it is preferred that the hotmelt glue applicator be fabricated in two main units. As particularlyshown at the bottom of FIGURE 1, there is provided a base plate 12having a bracket 13 secured thereto and supporting the feed body 14 of aglue supplier. Detachably mounted in an upstanding throat 16 formingpart of the feed mechanism in a light metal hopper 17 open at the topand designed to receive cold glue. This material is capable of changingfrom dry, granular or flaky condition when cold to a moderately viscousliquid when hot. Dry glue in the hopper 17 flows by gravity into thethroat 16. Means are provided for advancing the dry glue from the throat16 into a generally circular cylindrical, horizontal feed housing 18 andtherein exerting pressure upon the glue.

The driving means includes an open, helical screw 21. Preferably, thescrew is formed as a helix from square section rod. While the helix isfree at one end, it extends through the housing 18 and is anchored to adrive shaft 23. Appropriate bushings 24 mount the drive shaft 23 forrotation in a hub 26 of the body 14. A gear 27 fast on the end of thedrive shaft 23 is in mesh with a gear 28 joined to one member 29 of afriction slip clutch 31. A facing 32 is interposed between the member 29and a driving disc 33. These members are axially urged together by aspring washer 34 held in position by an adjusting nut 36 engaging adrive shaft 37 on the end of a reduction gear unit 38. An electric motor39 turns the shaft 37 and unless the load is excessive, transmits rotaryforce through the friction members and the gears to the shaft 23 and thehelix 21. In the event of overload, then the clutch slips and themechanism is not injured. When the clutch slips for a considerable time,the local temperature is elevated and the heat affects the surroundings.To preclude premature heating of the glue, the slipping clutch isdisposed on the motor shaft rather than on the drive shaft 23. Sincethere is good thermal isolation by the gears 27 and 28, the clutch heatdoes not disturb the glue.

As the helix 21 revolves, the dry, granular glue is on gaged by theconvolutions of the helix. To make sure that the helix serves as aneffective driver, the mass of glue is restrained from revolving with thehelix by irregularities on the interior of the housing 18 such asaxially extending splines 40. Thus, when the helix turns, the body ofglue is advanced along the axis of the housing 18, building up somepressure as it does so. The tendency of the helix is to compact the glueinto a dense body within the housing. There is no backflow even thoughthe pressure at the leading portion of the body of glue is considerable.The term flow is utilized in connection with the granular material,since this behaves largely as a liquid although it is actually in a dry,flaky or granular form.

Coupled to the feeding mechanism is a liquefying unit 41. The liquefyingunit 41 includes a massive metal body 42 of good heat conductingmaterial such as cast aluminum and is provided with an interior tortuouschannel 43 preferably in the form of a helix generated about an axis 44.The upper portion of the helix merges with an opening 46 serving as aninlet to the housing 18. Since it is desired to maintain good thermalisolation between the liquefying unit and the feeding unit, there isprovided a thermally insulating hose 47, having some flexibility,connected between these units. The hose is clamped in place by bands 48and 49 and itself surrounds part of the helix to serve as a part of oras a continuation of the cylindrical housing 18.

Part of the tortuous passage 43 is closed at its upper end by a plate 51having a peripheral seal 53 and secured by a central bolt 52. Thetortuous passage 43 winds downwardly from its inlet and extends into achamber 54 having a clean-out plug 56 closing one end thereof.Insulating securing bolts 57 and 58 pass through the base plate 12 andengages the body 42 to provide a firm mounting.

Arranged in the body 42, preferably crossing the axis 44 and in effectenveloped by the convolutions of the helical, tortuous passageway 43 isa bore 59. A heating element 61 having a conductor 62 extending to asuitable source of electricity is in elfect buried within the body andwhen energized transmits substantially all of its heat to thesurrounding metal for transference to the walls of the passage 43, thusincreasing the temperature of the material advanced through the passageby the operation of the feed screw 21. A standard temperature responsivecontroller 63 controls the operation of the heater 61. A thermalinsulating blanket 64 overlies portions of the body 42 and is covered bya protecting jacket 65.

The temperature imparted to the glue within the body 42 is sufficient toliquefy the glue but is considerably below a proper temperature for glueapplication. Most of the glues utilized with this apparatus tend tocook, caramelize and form deleterious deposits as a function oftemperature and time. Since it requires considerable time even atmaximum output for the glue to travel through the machine, itstemperature is kept as low as possible at the beginning of the flow andheat to application temperature is gradually applied as the glueadvances through the machine so that the higher temperatures areeffective over unimportant time periods.

By the time the relatively dry and solid glue has been advanced throughthe inlet 46 and has traveled at least part way through the tortuouspassage in close thermal relationship with the heater element 61, thematerial has increased in temperature sufficiently to liquefy and becomea continuous mass. The flow of the mass of now liquid glue thencontinues through the chamber 54. Flow cannot proceed toward the inletbecause of the presence of an advancing body of dry glue impelled by therotating helix. Flow of the liquid glue is thus into an outletpassageway 66 extending to a filter chamber 68 arranged vertically andhaving a closure plug 69 at the upper end thereof. Axially withdrawablefrom the filter chamber is a filter 71 having a peripheral screen 72reinforced by an interior spring 73 and disposed between a pair of heads74 and 75. The filter can be introduced and withdrawn as a body and isarrange in the path of flow of the melted glue so that all of the gluemust flow through the filter and emerges therefrom clean. A drain valve76 is located at the bottom of the chamber 68.

An outlet 77 from the body 42 is afforded through a connector 78 at oneend of a flexible tube 79. This tube is a good thermal conductor and isjacketed with a flexible insulating material 80-. A heating wire 85connected to a source of electricity is embedded within the jacket inconducting relationship to the tube 79 so that the temperature ofthe-material flowing therethrough is at least maintained and preferablyis augmened. In this fashion, the viscosity of the heated, liquid glueis controlled after it leaves the passage or chamber 68.

i The other end of the flexible tube 79 extends to an applicator unit asshown in FIGURES 1 and 5, particularly. In this unit there is provided amounting frame 81 suitably attached to the frame of the carton machineand including a clamp 82 grasping a tubular frame portion 83.

Rotatably mounted in a bushing 84 installed in the frame 83 is a drivingshaft 86. At the outboard end of this shaft there is mounted a sprocket87 adapted to be joined to the mechanism of the carton machine forrotation substantially in synchronism therewith. To avoid damage fromoverload, the sprocket 87 is not firmly connected to the shaft 86, butis freely journalled thereon and is driven through a ball 88 lodged in adriven disc 89 keyed to the shaft. The ball is pressed into a depression90 in the sprocket 87 by a leaf spring 91, the assembly being secured bya central bolt 92. While the sprocket 87 and the shaft 86 normallyrevolve together, in the event of shaft overload, the ball 88 rides outof the socket 90 to release the drive.

At its inboard end, the shaft 86- carries a glue applicator or patternwheel 94. This wheel includes a central hub 96 secured to the shaft 86by an end bolt 97 and likewise includes a thin, peripheral band 98. Thisgenerally has a circular cylindrical exterior configuration and isspaced from the hub 96 to leave a semi-enclosed annular volume. Theperiphery of the wheel is for the most part truly circular cylindrical,but at intervals is provided with depressions 99 arranged in anysuitable pattern, as desired, for the deposit of the melted glue on thecarton flap 7.

In order to maintain and control the temperature of the pattern wheel,the interior annular volume thereof is largely occupied by a heater cage101 at appropriately spaced points carrying a plurality of electricheaters 102 each having conductors 103 extending to a suitable source ofelectricity. The heaters and some of the attendant structure areappropriately held in position surrounding the tube 83 by insulatingmountings 104 into which securing bolts 106 extend from a flange 107 onthe tube 83.

In order to supply the glue pattern wheel with liquid glue at theappropriate, final temperature, a glue reservoir 111 is mounted on andextended from the frame. This reservoir is relatively small so that thetemperature of the stored glue can easily be controlled and will beuniform. Heat is transferred to the reservoir walls and to the containedglue through the periphery of the wheel 94 from the heaters 102. Thereservoir is formedof a bottom wall 112, side walls 113 and 114 and anend wall 116.. The reservoir is at atmospheric pressure and is tightlyrelated to the pattern wheel on and in alignment with the wall 114 by anapplied thin plate of springy material 117. This is held in position byremovable fastenings 118 so that there is virtually no leakage possible,between the plate 117 and the end face 119 of the pattern wheel. Thereservoir is smaller then the glue pattern wheel so that either the topor bottom periphery of the pattern wheel can be brought against thematerial to receive the glue.

Somewhat similarly, the wall 112 is extended and leakage is largelyprevented by the provision of a flexible, spring steel doctor blade 121resting against the bottom wall 112 and slightly sprung into tight contat with the periphery of the pattern wheel. The mounting and adjustmentof the doctor blade 121 are arranged by a slide 122 adjustably securedto the frame of the device. The slide 122 has elongated slots 123therein through which fastenings 124 extend. The slide also has an endridge 126 designed to abut tightly against the doctor blade.Furthermore, the slide has an L end 127 through which bolts 128 extendand are screwed into the main body of the reservoir. When the fastenings124 are loose, the bolts 12 8 can be operated to move the slide 122toward the pattern wheel. A shoulder 129 on the slide abuts the end ofthe doctor blade and moves it toward the pattern wheel. When anappropriate position of adjustment has been arranged, the bolts 124 aretightened to hold the parts in position. The spring rate of the blade121 is relatively high so that Bernouilli forces exerted between thepattern wheel 94 and the doctor blade during operation are resisted andno substantial leakage occurs.

The liquid, heated glue flowing through the heated, flexible line 79passes through a drilled channel 131 in the body of the reservoir anddischarges through lateral openings 132 into the reservoir.

Since it is desired to maintain substantially a predetermined level ofglue in the reservoir despite variations in the speed with which theglue is Withdrawn by rotation of the pattern Wheel, there is mounted inthe wall 116 a device responsive to level by sensing the temperature ofthe liquid glue in thermal contact with the device. For this reason thewall 116 is provided with an opening 133 communicating with the interiorof the reservoir and partially sealed by an insulating Washer 134clamped in place by a ring 136. Mounted on a separate plate 137thermally distinct from or isolated from the reservoir is the probe 138of a temperature responsive thermocouple or thermistor protected by ahood 139 and having a connection 141 for conductors leading to a controlstation, not shown.

When the level of the glue in the reservoir is low, the end of thesensing device 138 is exposed to the atmosphere and its temperature isrelatively low. This initiates or increases the flow of material throughthe heating element of FIGURE 2 and through the connecting flexible hoseto the reservoir. When suflicient glue has been received in thereservoir so that the level rises to the desired point, then thetemperature of the sensing device 138 rises and the supply of glue iscut down or stopped. Thus, there is an automatic sensing arrangement formaintaining the desired glue level in the reservoir.

In the operation of this device, when the carton mechanism is running,all of the circuits are conditioned so that the motor 39 is energizedand the feeding screw 21 is operated. The dry, pulverulent glue is thenadvanced in the form of a pressure compacted mass through the feedingportion of the machine and into the liquefying portion. The heater coil61 therein converts the dry, solid glue into liquid form as it traversesthe tortuous passage. After the glue has been filtered and has emergedfrom the chamber 68, it flows through the heated flexible hose to theapplicator unit. The glue temperature is maintained or augmented. Theglue forms a pool within the reservoir maintained at proper, preferablyhigher temperature, being retained by the reservoir walls andparticularly by the doctor blade 121 and the side plate 117. Therotating wheel circulates the glue in the reservoir and tends tomaintain a uniform temperature throughout the glue pool. The desiredlevel of liquid glue in the reservoir is auto matically sustained.

Upon rotation of the sprocket 87, the shaft 86 is revolved and theapplicator wheel likewise turns. As the periphery of the applicatorwheel traverses the reservoir in contact with the glue therein, certainvolumes of glue are trapped or lodged within the depressions 99 of theapplicator wheel, any surplus being scraped off by the doctor blade.This glue is in close thermal contact with the heaters and is brought upto final temperature. The periphery of the applicator wheel is free ofglue except in the depressions 99. As the applicator or pattern Wheelrevolves in abutment with the tangent flap 7 of the carton, discretebodies of liquid glue are deposited thereon. This flap promptly isadvanced in the machine by the carton mechanism. The rotating patternwheel depressions, being emptied of carried glue, then traverses thereservoir again, picking up further glue charges for subsequent cartonflaps.

The glue on the pattern wheel that does not adhere to the carton flapsis returned by further rotation of the wheel to the reservoir, beingdirected to flow inwardly thereto by bevels 142 along the top edges ofthe side walls 113 and 114 of the reservoir. Thus, no glue is lost andthat not applied is reheated and recircu ated.

What is claimed is:

1. A hot melt glue applicator comprising a frame, a glue reservoir openat the top and on one end, means for mounting said glue reservoir onsaid frame, an applicator wheel, means for journalling said applicatorwheel on said frame in position to form a Wall for said one end of saidreservoir, said applicator Wheel being shaped to define an annularvolume, a heater, means for mounting said heater stationarily on saidframe within said volume, to transmit heat through said applicator Wheelto said reservoir, means responsive to temperature mounted on said frameand extending into the interior of said reservoir, and means controlledby said temperature responsive means for supplying said reservoir withhot liquid glue.

2. A hot melt glue applicator comprising a frame, a glue reservoir onsaid frame, said glue reservoir including a bottom wall and a pair ofside walls at one end terminating in arcuate edges and at the other endterminating in an end wall having an opening therein, an applicatorWheel rotatably mounted on said frame with the pe riphery of said wheelmaking a close running fit with said edges, said applicator wheel havinga thin peripheral band to define an annular volume, a heater fixed onsaid frame and disposed in said volume in thermal relationship with saidwheel and with said reservoir through said band, means for supplyingsaid reservoir with liquid glue, means on said frame thermally remotefrom said heater for supporting a temperature responsive device, atemperature responsive device on said supporting means and extendingthrough said opening, and means for controlling said supplying means bysaid temperature responsive device.

3. A hot melt glue applicator comprising a tubular frame, a drivingshaft journalled in and extending from said frame, a pattern wheelmounted on said shaft, said pattern wheel having a thin peripheral bandsurrounding but spaced from said tubular frame to leave an interveningannular volume, a heater frame including a heater cage substantiallyoccupying said volume, means for supporting said heater framestationarily on said tubular frame, a glue reservoir mounted on saidheater frame at one side of said pattern wheel and having side wallsextending substantially to the edges of said peripheral band leaving thecentral portion of said band exposed to the interior of said reservoir,and heaters in said heater cage and constituting the sole source of heatfor said reservoir.

4. A device as in claim 3 in which said supporting means includes athermal insulator for isolating said heater frame from said tubularframe.

5. A device as in claim 3 in which said reservoir has a heightsubstantially less than the diameter of said pattern wheel whereby boththe top and bottom of said pattern wheel can be contacted by horizontalsheets overlying and underlying said glue reservoir.

References Cited UNITED STATES PATENTS 2,861,159 11/1958 Seney 137-392 X2,912,959 11/1959 Showalter 1185 3,030,915 4/1962 Shannon ll8-2023,028,833 4/1962 Hummel 118-7 3,206,125 9/1965 Farrell 2l9301 X3,255,727 6/1966 Boothroyd 1l87 FOREIGN PATENTS 901,592 7/ 1962 GreatBritain.

CHARLES A. WILLMUTH, Primary Examiner. L. G. MACHLIN, AssistantExaminer,

1. A HOT MELT GLUE APPLICATOR COMPRISING A FRAME, A GLUE RESERVOIR OPENAT THE TOP AND ON ONE END, MEANS FOR MOUNTING SAID FLUE RESERVOIR ONSAID FRAME, AN APPLICATOR WHEEL, MEANS FOR JOURNALLING SAID APPLICATORWHEEL ON SAID FRAME IN POSITION TO FORM A WALL FOR SAID ONE END OF SAIDRESERVOIR, SAID APPLICATOR WHEEL BEING SHAPED TO DEFINE AN ANNULARVOLUME, A HEATER, MEANS FOR MOUNTING SAID HEATER STATIONARILY ON SAIDFRAME WITHIN SAID VOLUME, TO TRANSMIT HEAT THROUGH SAID APPLICATOR WHEELTO SAID RESERVOIR, MEANS RESPONSIVE TO TEMPERATURE MOUNTED ON SAID FRAMEAND EXTENDING INTO THE INTERIOR OF SAID RESERVOIR, AND MEANS CONTROLLEDBY SAID TEMPERATURE RESPONSIVE MEANS FOR SUPPLYING SAID RESERVOIR WITHHOT LIQUID GLUE.